Our long term objective is to achieve an understanding of the complex organization of the seminiferous epithelium, in particular, the structure-function relationships of Sertoli cells and germ cells. We plan to continue this interest emphasizing the inter-dependence of Sertoli and germ cells. The Sertoli cell is well endowed with an impressive array of cytoplasmic filaments. Using morphological and biochemical methodologies, we plan to provide information concerning the role of these filaments in various functions of the Sertoli cell in the control of germ cell differentiation. Several of our experiments will be carried out on cultured Sertoli cells. A principal objective of our research is to attempt to grow Sertoli cells on defined substrates so that they will more closely resemble the columnar shape of their "in vivo" counterparts. A second aspect of our work concerns studies on alpha lactalbumin. This important milk protein has been found recently in testis and epididymis and may have a role in sperm-egg binding. We have highly purified antisera to alpha lactalbumin and will use immunocytochemical procedures to localize this protein more precisely in testis and epididymis. We have recently developed a radioimmunoassay for alpha lactalbumin. Our objective in this part of the work is to determine the importance of alpha lactalbumin in male reproductive function. The topic of endocytosis is a major interest in our laboratory. Macromolecules from the blood must enter the Sertoli cells and then be transported to germ cells. We wish to examine the mechanism of the endocytosis. Androgen binding protein (ABP), a secretory product of Sertoli cells, is endocytosed by the epididymal cells. We will examine the mechanism of uptake of ABP, and other proteins, by the epididymis. These experiments may provide information on the role of ABP in sperm maturation.